Method, system and apparatus for estimation of propagation path variability of a transmit diversity channel

ABSTRACT

A method and apparatus for dynamic adaptation of transmit diversity parameters according to detected dynamics that may be, for example, related to changes in actual propagation and network conditions, and may be referred to as mobility parameters. Mobility parameters may apply to variability in a propagation path due to any conditions. Determination of a mobility parameter may be conducted using one or more of multiple parameters available to the mobile terminal.

FIELD OF THE INVENTION

The present invention relates to wireless transmit diversity, and inparticular to methods, systems and apparatus for control of transmitdiversity in wireless systems.

BACKGROUND OF THE INVENTION

Wireless transmission systems may use transmit diversity, wherebysignals are transmitted to a receiver using a plurality of transmitantennas. Typically, such transmit diversity systems are intended toincrease network capacity and reduce the signal degradation caused bymulti-path and fading. Transmit diversity parameters may be applied tosignals transmitted from two or more antennas, and may modify aneffective power distribution detected: by receivers, such as basestations. A signal quality received may change at a receiver that may beattempting to detect a transmission from a mobile terminal, as well as anoise level created by a wireless terminal transmission in base stationsattempting to detect signals from other wireless terminals. A signal tonoise ratio perceived by a base stations may change with varyingparameters of transmit diversity control.

SUMMARY OF EMBODIMENTS OF THE INVENTION

Transmit diversity performance may be measured with respect to certainparameters, such as transmit power, throughput, system capacity andcoverage. Transmit diversity control algorithms have parameters that mayprovide different performance under different operational conditions.When propagation conditions are stable or vary slowly, small changes ofparameters around values previously defined may provide good performanceand more stable operation and maximize benefits of transmit diversitycontrol. In a dynamic environment, such as when a mobile terminal may bemoving or other objects cause variations of the propagation path betweena transmitter and a receiver, transmit diversity control may achieveimproved performance by, for example, allowing a larger change inalgorithm parameters. A parameter may be, for example, a step size in aphase difference between transmitted signals or may be a smallerinterval between changes in parameters. A faster rate of change of aparameter may allow faster adaptation of a transmit diversity controlparameter to a varying propagation condition.

Embodiments of the present invention include a method and apparatus fordynamic adaptation of transmit diversity parameters according todetected dynamics that may be, for example, related to changes in actualpropagation and network conditions, and may be referred to as mobilityparameters. Mobility parameters may apply to variability in apropagation path due to any conditions. Determination of a mobilityparameter may be conducted using one or more of multiple parametersavailable to the mobile terminal.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter regarded as the invention is particularly pointed outand distinctly claimed in the concluding portion of the specification.The invention, however, both as to organization and method of operation,together with objects, features, and advantages thereof, may best beunderstood by reference to the following detailed description when readwith the accompanying drawings in which:

FIG. 1 is a schematic block diagram of a communication network accordingto an embodiment of the present invention that includes one or moretransmitting communication devices and one or more receivingcommunication devices that communicate via a wireless link;

FIG. 2 is a flowchart illustrating a method for computing mobilityparameters using a threshold according to an embodiment of the presentinvention;

FIG. 3 is a flowchart illustrating a method for computing mobilityparameters using values according to an embodiment of the presentinvention;

FIG. 4 is a table of mobility values according to an embodiment of thepresent invention; and

FIG. 5 is a flowchart illustrating a method for computing diversityparameters according to an embodiment of the present invention.

It will be appreciated that for simplicity and clarity of illustration,elements shown in the figures have not necessarily been drawn to scale.For example, the dimensions of some of the elements may be exaggeratedrelative to other elements for clarity. Further, where consideredappropriate, reference numerals may be repeated among the figures toindicate corresponding or analogous elements.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS OF THE PRESENT INVENTION

Embodiments of the present invention may allow for transmit diversitycontrol by using a system that uses selection of phase parameters toenhance the system throughput, by requiring less repetitions orsupporting higher data rate and larger, more efficient data packets.Embodiments of the present invention may allow for a system with reducedpower consumption by providing control of the power ratio, or relativeamplitude, the relative phase, or both, of output signals. Embodimentsof the present invention may allow for improvement of power efficiency,optimized received signal quality, or both, by maintaining high radiofrequency (RF) linearity through an air interface with a defined powerrange. Embodiments of the present invention may allow for improvement ofthe effects of switching transients by providing improved phase shiftschemes. Embodiments of the present invention may allow for improvementof routing by providing improved switch configurations.

Embodiments of the invention may provide for improved performance,measured, for example, in terms of the power the unit is required totransmit for the receiver to receive acceptable signal quality, thenumber of errors in the transmission, higher throughput and improvedcoverage resulting from possibly improved selection of diversity controlparameters.

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the invention.However, it will be understood by those skilled in the art that thepresent invention may be practiced without these specific details. Inother instances, well-known methods, procedures, and components have notbeen described in detail so as not to obscure the present invention.

Embodiments of the present invention and its advantages are bestunderstood by reference to FIGS. 1 through 5, like numerals being usedfor like and corresponding parts of the various drawings; however, itwill be understood that the figures depict examples and embodiments onlyand do not limit the scope of the present invention.

FIG. 1 is a block diagram illustrating a communication network 10according to an embodiment of the present invention that includes amodifying communication device 20 a that that adjusts a nominal value ofa transmit diversity parameter. According to the embodiment, modifyingcommunication device 20 a may compute a diversity parameter that is usedto control the power, phase, or both, of transmit diversity for a signaltransmitted from communication device 20 a to receiving communicationdevice 20 b. Modifying communication device 20 a may adjust a nominalvalue of transmit diversity parameter based on the adjustment of thephase, power, or both parameters.

According to the illustrated embodiment, network 10 may operate toprovide services such as communication sessions. A communication sessionmay refer to an active communication between endpoints, measured fromendpoint to endpoint. Information is communicated during a communicationsession. Information may refer to voice, data, text, audio, video,multimedia, control, signaling, other information, or any combination ofthe preceding.

The information may be communicated in packets. A packet may comprise abundle of data organized in a specific way for transmission, and a framemay comprise the payload of one or more packets organized in a specificway for transmission. A packet-based communication protocol such asInternet Protocol (IP) may be used to communicate the packets. A packetmay comprise any suitable packet, such as a General Packet Radio Service(GPRS) packet, an Enhanced Data for GSM Evolutions (EDGE) packet, orother suitable packet.

Network 10 may utilize communication protocols and technologies toprovide the communication sessions. Examples of communication protocolsand technologies include those set by the Institute of Electrical andElectronics Engineers, Inc. (IEEE) 802.xx standards, InternationalTelecommunications Union (ITU-T) standards, European TelecommunicationsStandards Institute (ETSI) standards, Internet Engineering Task ForceIETF) standards, or other standards.

Devices of network 10 may use any suitable multiple access technology,for example, a code division multiple access (CDMA) technology.According to one embodiment, network 10 may operate according to a CDMA2000 telecommunications technology that uses a single CDMA channel. Asan example, a CDMA 2000 high rate data packet technology, such as theEvolution Data Only (EvDO) technology may be used.

Network 10 may comprise any suitable communication network. Acommunication network may comprise all or a portion of a public switchedtelephone network (PSTN), a public or private data network, a local areanetwork (LAN), a metropolitan area network (MAN), a wide area network(WAN), a global computer network such as the Internet, a wireline orwireless network, a local, regional, or global communication network, anenterprise intranet, other suitable communication link, or anycombination of the preceding.

A component of network 10 may include logic, an interface, memory, othercomponent, or any suitable combination of the preceding. “Logic” mayrefer to hardware, software, other logic, or any suitable combination ofthe preceding. Certain logic may manage the operation of a device, andmay comprise, for example, a processor. “Interface” may refer to logicof a device operable to receive input for the device, send output fromthe device, perform suitable processing of the input or output or both,or any combination of the preceding, and may comprise one or more ports,conversion software, or both. “Memory” may refer to logic operable tostore and facilitate retrieval of information, and may comprise a RandomAccess Memory (RAM), a Read Only Memory (ROM), a magnetic drive, a diskdrive, a Compact Disk (CD) drive, a Digital Video Disk (DVD) drive, aremovable media storage, any other suitable data storage medium, or acombination of any of the preceding.

Communication network 10 may include one or more modifying communicationdevices 20 a and one or more communication devices 20 b that communicatevia a wireless link 24. Either or both of communication devices 20 a or20 b may be any device operable to communicate information via signalswith one or more other communication devices. For example, communicationdevice 20 a or 20 b may comprise a subscriber unit or a base station. Asubscriber unit may comprise any device operable to communicate with abase station, for example, a personal digital assistant, a cellulartelephone, a mobile handset, a computer, or any other device suitablefor communicating signals to and from a base station. A subscriber unitmay support, for example, Session Initiation Protocol (SIP), InternetProtocol (IP), or any other suitable communication protocol.

A base station provides a subscriber unit access to a communicationnetwork that allows the subscriber unit to communicate with othernetworks or devices. A base station typically includes a basetransceiver station and a base station controller. The base transceiverstation communicates signals to and from one or more subscriber units.The base station controller manages the operation of the basetransceiver station.

Either or both of communication devices 20 a or 20 b may include one ormore antenna elements, where each antenna element is operable toreceive, transmit, or both receive and transmit a signal. Multipleantenna elements may provide for a separation process known as spatialfiltering, which may enhance spectral efficiency, allowing for moreusers to be served simultaneously over a given frequency band.

A communication link between communication devices 20 a and 20 b such aswireless link 24 may be a radio frequency link that is cellular innetwork organization. Wireless link 24 may be used to communicate asignal between communication devices 20 a and 20 b.

As described more fully below, according to embodiments of the presentinvention, modifying communication device 20 a may include a signalmodifier 32 a that modifies one or more signals. Signal modifier 32 amay then modify the transmit signal in accordance with selection ofphase, power, or both, diversity parameters.

According to one embodiment of the invention, modifying a signal mayrefer to modifying a signal feature. A transmission signal feature, orin some embodiments of the invention, a transmit diversity parameter,may refer without limitation to any feature of the transmission, forexample, relative phase, relative amplitude, relative power, absolutepower, frequency, timing, other suitable signal feature that may bemodulated, or any combination of the preceding. Relative phase may referto the phase difference between the phase of a first signal of a firsttransmit antenna element and the phase of a second signal of a secondtransmit antenna element. Relative power may refer to the ratio betweenthe power of a first signal of a first transmit antenna element and thepower of a second signal of a second transmit antenna element, whichratio may be defined on a linear or logarithmic scale. Relativeamplitude may refer to the ratio between the amplitude of a first signalof a first transmit antenna element and the amplitude of a second signalof a second transmit antenna element. Absolute power may refer to thetotal power transmitted by all antennas of modifying communicationdevice 20 a. According to one embodiment, modifying a signal may bedescribed as adjusting a nominal value of a transmit diversityparameter. As described more fully herein, according to an embodiment ofthe invention, adjustment of a transmit diversity parameter may compriseselecting phase diversity parameters, selecting power diversityparameters, or both.

A modifying communication device 20 a calculates transmit diversityparameters for use in transmitting across wireless link 24. Modifyingcommunications device 20 a may modify transmit diversity parameters fortransmission to receiving communication device 20 b using phasediversity parameters, power diversity parameters, or both.

In some embodiments of the device, modifying communication device 20 amay include a transmit signal control and a signal modifier. Qualityindication generator 30 a may generate parameters used for controllingtransmit diversity of modifying communication device 20 a. Theparameters may be generated by any suitable manner, for example, basedon feedback from the receiving communication device 20 b, actualenvironmental conditions at the modifying communication device 20 a, oneor more performance parameters measured at modifying communicationdevice 20 a, or other indications. Signal modifier 32 a may modify apre-transmission signal in accordance with one or more transmitdiversity parameters obtained from quality indication generator 30 a.

Alterations or permutations such as modifications, additions, oromissions may be made to communication network 10 without departing fromthe scope of the invention. Additionally, operations of communicationnetwork 10 may be performed using any suitable logic comprisingsoftware, hardware, other logic, or any suitable combination of thepreceding.

In one embodiment of the present invention, mobility parameters may bebased on power control signals. These signals may be power controlcommands that may be transmitted by a base station and may be receivedby a terminal. The signal may include a command to increase or reducetransmitted power of a mobile station. During some transmissionconditions that may allow for stable propagation conditions, a variationin pilot channel power that the mobile terminal may be required tocontrol may be small. In other conditions, for example when propagationconditions may become less stable, a transmission condition, forexample, a path loss between a base station and a mobile terminal maybecome highly variable. In this case, the uplink power control mayreflect this variation by requesting a larger change in a mobiletransmit power.

In an embodiment of the present invention, mobility parameters may bebased on a detection of a received power level mobility on the downlink.A mobile terminal may detect transmission of one or multiple basestations; When the propagation conditions are stable, a detected powerlevel may be relatively stable. When the dynamics of the propagationincrease, a rate of change of a received power level may increase.

An embodiment of the present invention may base mobility detection onactual feedback from a base station, and may indicate a change inconditions. A base station may measure a signal level from a mobileterminal, and may determine, from multiple measurements over time, avariability of an uplink propagation path. A base station may send to amobile terminal, either as part of a standard, if allowed, or as ahigher level message, an indication of variability level of apropagation path.

Additional embodiments of the present invention may include anycombination of any of these embodiments, and/or that may allow for thedetermination of additional mobility parameters.

FIG. 2 is a flowchart illustrating a method for computing mobilityparameters using a threshold according to an embodiment of the presentinvention. This method applies a difference in power to detect changesin dynamics of propagation. The method may be executed at intervals,which may be every time a new input is received, or at larger intervalsthat may correlate to a lower rate, as it may not be necessary tocompute dynamics of a propagation path at a maximum rate. The method maydetermine variation of power within a window, which may include multipleslots, and may be measured in time units that may correspond to an airinterface. A variation may include, refer to, or correspond to adifference between a maximum and a minimum power within a window, whichmay require more sampling and processing, or a difference between apower at the end of a window and the power at its beginning. A slot inW-CDMA is approximately 667 μsec, in cdma2000 1× it is 1.25 msec, inEvDO it is approximately 1.67 msec. A window may for example beequivalent to the duration of 16 slots. Different power differences mayapply to various embodiments of the present invention.

In one embodiment of the invention, a power difference may be anaddition of reverse power control-bits (PCB) in a window, or adifference between a maximum and a minimum pilot power transmittedduring a window, or an actual pilot power during a last slot of awindow, less actual pilot power during a first slot of the window.

In an embodiment of the invention, a power difference may be adifference between a maximum and a minimum pilot power in signalsreceived from a base station, that may be received with highest power,or may be between a maximum and a minimum total pilot power, where inboth cases a pilot power may be computed multiple times within a window,for example, in every slot.

In an embodiment of the invention, a power difference may be between amaximum and a minimum pilot power in a mobile terminal uplink signalthat may be received by a base station during a window, or a differencebetween a pilot power received during a previous slot of a window and apilot power during a first slot of the window.

A mobility parameter that may be used may be a measure of signalquality, for example, a standard deviation of a signal quality of areceived parameter across a window. This parameter may be used, forexample, in lieu or in addition to a power difference. Other powerdifferences or other similar parameters may be selected within the scopeof this invention.

In an embodiment, a number N of slots may represent a window size. Aninterval between computations may be designated as INTERVAL1 orINTERVAL2, and may comprise similar or different values. An algorithmthreshold that may be used to determine variability within a window maybe designated THRESH1. A maximum allowable value for a mobilityparameter may be designated MAX_MOBILITY, and a minimum allowable valuefor a mobility parameter may be designated MIN_MOBILITY.

Referring to FIG. 2, the mobility parameters may be set to initialvalues in step 110. When an interval includes a certain number of slots,a SLOT variable may be defined, and may be increased, modulo the numberof slots INTERVAL in a selected interval. For example, SLOT=0 may set aparameter to the beginning of a window, and MOBILITY=0 may set aninitial mobility parameter. In step 120 it is determined whether it istime to compute a new MOBILITY value, in accordance with the presentvalue of the computation interval. The present interval may be set to aconstant value or may be variably set to different values. The SLOTvariable may be increased, for example, by the formula SLOT=(SLOT+1) modINTERVAL. If an interval condition is met, and a computation interval iscomplete, for example when SLOT=0, the algorithm continues to step 130.If the condition is not met, for example when SLOT>0, the algorithm maynot perform any computation, and may return to the input of step 120,where it will next test for completion of an interval, for exampleduring the next slot.

In step 130, the selected power difference may be computed inside awindow. If a power difference is an uplink pilot power change across awindow, it may be computed by adding the N most recent PCB's, and eachPCB may be assigned a corresponding power change value. In W-CDMA (UMTS)PCB=0 may be assigned a value of +1 and PCB=1 may be assigned a value of−1, and in cdma2000 PCB=0 may be assigned a value of −1 and PCB=1 may beassigned a value of +1.

In step 140, a power difference may be compared with a threshold. In theillustrated embodiment, a threshold may be assumed to be symmetrical,and an absolute value of a power difference may be used to determine ifa single threshold THRESH1 is exceeded. For example, when there are more+1 inputs than −1 inputs, the accumulation may exceed +THRESH1 and whenthere are more −1 inputs than +1 inputs, the accumulation may yield amore negative result than −THRESH1. If an absolute power differenceexceeds a threshold, the algorithm continues to step 150. If an absolutepower difference does not exceed the threshold, the algorithm continuesto step 170.

In step 150 a mobility parameter MOBILITY may be increased, up to amaximum MAX_MOBILITY, for example, MOBILITY=min{MOBILITY+STEP1,MAX_MOBILITY}. The determination of a new MOBILITY parameter may becompleted. The method may proceed to step 160, where a first mobilityinterval parameter may be changed. In one embodiment, the parameter maybe set to INTERVAL1, which may correspond to an increase in a MOBILITYparameter. The method may then return to step 120 to await the nextcomputation.

In step 170 a mobility parameter MOBILITY may be decreased. In anembodiment, the parameter may be reduced by a decay factor DECAY, forexample, MOBILITY=MOBILITY×DECAY. In another embodiment, the parametermay be reduced linearly down to a limit, for example,MOBILlTY=min{MOBILITY−STEP2, MIN_MOBILITY}. A determination of a newMOBILITY parameter may be completed. The algorithm may proceed to step180, where a second interval may be changed. In one embodiment, theparameter may be set to INTERVAL2, which may correspond to a reductionin a MOBILITY parameter. The method may then return to step 120 to awaitthe next computation.

Upon calculating the mobility interval parameter, at least one transmitdiversity parameter may be modified based thereupon, for example, stepsize, offset, perturbation rate, etc. In one embodiment, when mobilityincreases, the method may increase at least one of step size, offset, orperturbation rate, and when mobility decreases, the method may decreaseat least one of step size, offset, or perturbation rate.

In one embodiment, values of the mobility interval parameters may be,for example, a computation interval after increasing MOBILITY parameter,INTERVAL1=8, a computation interval after decreasing MOBILITY parameter,INTERVAL2=4, window size, or number of inputs for which a singlecomputation may be made N=16, power threshold for 1 dB PCB's THRESH1=12,mobility parameter step size STEP1=0.47, and decay factor DECAY=0.999.It will be understood that the values provided are particular examples,and that other values and parameters may be used within the scope of theinvention.

FIG. 3 is a flowchart illustrating a method for computing a mobilityparameter according to a soft in window mobility detection algorithm.This soft algorithm may allow assignment of multiple values, forexample, grades, to this power difference. This method may increaseflexibility, relative to the threshold method. The grade may represent apower difference within a range of possible values. A grade may beassociated with a specific power difference or with a range of powerdifferences. A grade may be added to a MOBILITY parameter, or parameterswhere multiple MOBILITY parameters may be computed.

In step 210, mobility parameters may be initialized. In step 220, it maybe determined whether it is time to compute a new MOBILITY value,according to the present interval. In step 230 a previous MOBILITY valuemay first be decreased, for example, to account for the additionalaging, before conditionally increasing it based on a specific powerdifference. A power difference may be computed in step 240. In step 250,a GRADE may be looked up per the value of the power difference from amemory. In step 260 a GRADE may be added to a MOBILITY parameter, and amobility parameter is computed. If GRADE=0, for example, MOBILITY maynot be increased. GRADE may be negative, and may, for example, lead to adecrease in MOBILITY, up to a minimum value. In step 270, an intervalparameter that may determine a next computation may be set. An intervalmay be constant, for example, and this step may be skipped. Theparameter may be a function of a difference in power, or may be afunction of a MOBILITY parameter. The algorithm then returns to step 120for the next computation.

An interpretation may be made to apply the mobility conditions to atransmit diversity control algorithm, for the value of a MOBILITYparameter and specific algorithm parameters may be selected. FIG. 4 is atable of an example of an embodiment of an interpretation. In thisembodiment, multiple ranges of a mobility value MOBILITY may beselected. The mobility values 310 are shown as an example of a possibleselection. A propagation path condition 320 may be associated with thesevalue ranges. For example, a propagation path condition 320 may rangefrom static, or most stable, to very high mobility, or fastest changing.A tracking step 330 of a transmit diversity parameter, for example astep controlling how fast diversity parameters may change, may beassigned step values 340. For example, a minimal step value 340 may be1, a low value may be 2, a medium value may be 3, a high value may be 5and a very high value may be 8.

FIG. 5 is a flowchart of a mobility application to an operation of atransmit diversity algorithm, that may allow for changes in propagationconditions. In step 410, the mobility parameters are computes accordingto an embodiment of the present invention. In step 420, a transmitdiversity algorithm is executed using modified parameters from themobility computation. In step 430 transmit diversity control parametersare implemented, as they may have been modified by the detectedpropagation conditions, and are output and applied to the signalmodifier transmit signals.

Another embodiment of the present invention may be Mobility computationsbased on a combination of embodiments. A first method of combination,for example, may be to apply the threshold method illustrated by FIG. 2to each input parameter separately, for example, each embodimentcomputes its own mobility factor. Then, the mobility factors generatedby the different active embodiments may be combined to form a singleMOBILITY factor.

A second method of combination may be to use a modified algorithm thatmay combine multiple input parameters previously used by separateembodiments into a single combined computation.

Both combination methods may be used alone, or in combination with eachother. For example, the second combination method may be applied togenerate a common mobility parameter based on two embodiments, and athird embodiment may yield a separate mobility parameter. This may beapplicable when inputs to different embodiments may be physicallyseparated, for example, when some inputs may be mobile terminalmeasurements and other inputs may be base station measurements. Amobility parameter computed by one embodiment may then be transmitted toa unit that may combine separate parameters.

Another combination embodiment may be where each embodiment may computea mobility parameter independently using the algorithm illustrated byFIG. 2. Then a first embodiment may output MOBILITY1, a secondembodiment may output MOBILITY2, and additional embodiments may haveadditional outputs, and for each parameter there may be separatemobility results. A single combined MOBILITY parameter may be determinedby modifying transmit diversity parameters, directly, or by weighting.For example, a linear weighting algorithm may be represented by:

MOBILITY=k1×MOBELITY1+k2×MOBILITY2+k3×MOBELITY3

In one example of an embodiment of equal weighting, the weights may bek1=k2=k3=⅓. Or, for example, when only using two parameters where thefirst is considered twice as reliable as the second, a weighting may bek1=⅔, k2=⅓, k3=0.

In an example of an embodiment, k1+k2+k3=1, and the same scale for allmobility values may be preserved. In an example of another embodiment,k1=3, k2=4, and k3=1 may also be selected. In an example of anotherembodiment, different weightings may be used to bring the differentmobility parameters to a common scale.

An example of an implementation may be by modifying step 230 of FIG. 2.In this modified implementation, the mobility parameter may be computedbased on multiple types of inputs. An example may be to combine a firstembodiment and a second embodiment, where a first embodiment may use amobile transmitted pilot power and, for example, may compute adifference in a power in a window, ΔPower1. A second embodiment may usea received downlink pilot power, and may compute a difference in a powerin a window, ΔPower2. In this example, the modified step 230 mayinclude:

ΔPower1(n)=Power1(n)−Power1(n−N+1)

ΔPower2(n)=Power2(n)−Power2(n−N+2)

ΔPower=k5×|ΔPower1(n)|+k6×|ΔPower2(n)|

where n may be a present time, N may be a window duration, and n and/orN may use units of slots, k5 and k6 are weighting factors. In oneexample k5=k6=0.5.

Another method of combining results from separate embodiments into acombined embodiment may be by Boolean combination. For example, aBoolean parameter LogicMOB which is TRUE when MOBILITY is higher thansome threshold and FALSE otherwise may be defined. There may be multipleparameters MOBILITYj, (j=1,2,3, . . . ) and the same may apply for allof them, with respective Boolean parameters LogicMobj associatedtherewith. Multiple Boolean functions may be defined. For example, onesuch combination may be a logical OR, which may apply to a TRUE /FALSEvalue of MOBILITY parameters:

LogicMOB=LogicMOB1 OR LogicMOB2 OR LogicMOB3

LogicMOB may be true if any of the measured separate parameters indicatevariability of a propagation path.In another example, a different logical operator AND may be used:

LogicMOB=LogicMOB1 AND LogicMOB2 AND LogicMOB3

which may render LogicMOB TRUE when all separate parameters may be TRUE.It will be recognized that any combination of logical operators may beused in conjunction with the present invention.

In another example of combining embodiments that may be applicable tonumerical values of the MOBILITY parameter, it may be defined to be amaximum of separate parameters:

MOBILTY=max{MOBILITY1, MOBILITY2, MOBILITY3}

A minimum of separate parameters may also be used in a similar fashion.

In another embodiment, more than one MOBILITY parameter using differentparameters such as STEP1, STEP2 and DECAY or different combinations ofseparate parameters may be computed, and these different MOBILITYparameters may be applied to control different parameters of a diversitycontrol algorithm. In this example, some algorithm steps may be made torespond faster to, for example, quick changes in propagation conditions,and another parameter, for example a computation interval, may be madeto respond slower.

Embodiments of the invention may apply to any transmit diversity controlmethod. It will be understood that the methods discussed herein may beintegrated with any transmit diversity control algorithm. It willfurther be understood that the present invention may be implemented as astand-alone processing module, or may be integrated into a transmitdiversity control processor, algorithm, or signal path circuitry.

While certain features of the invention have been illustrated anddescribed herein, many modifications, substitutions, changes, andequivalents will now occur to those of ordinary skill in the art. It is,therefore, to be understood that the appended claims are intended tocover all such modifications and changes as fall within the true spiritof the invention.

1. A transmit diversity communication method comprising: calculating ata first device at least one mobility parameter, said mobility parameterindicating alteration in propagation of a signal transmitted betweensaid first device and a second device; calculating based on said atleast one mobility parameter at least one diversity parameter; andtransmitting a transmit diversity signal from said first device usingsaid at least one diversity parameter.
 2. The transmit diversity methodof claim 1, wherein calculating said at least one mobility parametercomprises calculating at least one power difference.
 3. The transmitdiversity method of claim 1, wherein said at least one power differenceis selected from the group consisting of: a difference between a minimumpower and a maximum power within a time window, a difference between afirst power and a last power within a time window.
 4. The transmitdiversity method of claim 3, wherein calculating said at least onemobility parameter comprises comparing said power difference to athreshold.
 5. The transmit diversity method of claim 4, whereincalculating said mobility parameter comprises incrementing a previousvalue of said mobility parameter if said power difference is greaterthan said threshold.
 6. The transmit diversity method of claim 5,wherein calculating said mobility parameter comprises decrementing aprevious value of said mobility parameter if said power difference isless than said threshold.
 7. The transmit diversity method of claim 4,further comprising repeatedly at time intervals calculating said atleast one mobility parameter and calculating said at least one diversityparameter.
 8. The transmit diversity method of claim 7, wherein saidtime intervals are based on said power difference.
 9. The transmitdiversity method of claim 8, wherein said time intervals are selectedfrom at least two constant time intervals based on said comparison ofsaid power difference to said threshold.
 10. The transmit diversitymethod of claim 1, wherein calculating said at least one diversityparameter based on said at least one mobility parameter comprisesincreasing a diversity interval parameter in a first direction based onan increase in said mobility parameter.
 11. The transmit diversitymethod of claim 10, wherein calculating said at least one diversityparameter based on said at least one mobility parameter comprisesincreasing said diversity interval parameter in said first direction ifsaid mobility parameter exceeds a threshold value.
 12. The transmitdiversity method of claim 10, wherein calculating said at least onediversity parameter based on said at least one mobility parametercomprises decreasing said diversity interval parameter in a seconddirection opposite said first direction based on a decrease in saidmobility parameter.
 13. The transmit diversity method of claim 12,wherein calculating said at least one diversity parameter based on saidat least one mobility parameter comprises decreasing said diversityinterval parameter in said second direction if said mobility parameterdoes not exceed a threshold value.
 14. A transmit diversitycommunication system comprising: a first communication device having aprocessor to calculate at a first device at least one mobilityparameter, said mobility parameter indicating alteration in propagationof a signal transmitted between said first device and a second device,to calculate based on said at least one mobility parameter at least onediversity parameter, a transmitter to transmit a diversity signal fromsaid first device using said at least one diversity parameter; and asecond communication device having a processor to calculate a qualityindication parameter relating to a signal received from said firstdevice, and a transmitter to transmit said quality indication signal tosaid first transmitter.
 15. The communication system of claim 14,wherein said processor of said first device is further to calculate atleast one power difference.
 16. The communication system of claim 15,wherein said at least one power difference is selected from the groupconsisting of: a difference between a minimum power and a maximum powerwithin a time window, a difference between a first power and a lastpower within a time window.
 17. The communication system of claim 16,wherein said processor of said first device is to compare said at leastone power difference to a threshold.
 18. The communication system ofclaim 17, wherein said processor of said first device is to increment aprevious value of said mobility parameter if said power difference isgreater than said threshold.
 19. The communication system of claim 18,wherein said processor of said first device is to decrement a previousvalue of said mobility parameter if said power difference is less thansaid threshold.
 20. The communication system of claim 17, furthercomprising repeatedly at time intervals calculating said at least onemobility parameter and calculating said at least one diversityparameter.
 21. The communication system of claim 20, wherein said timeintervals are based on said power difference.
 22. The communicationsystem of claim 21, wherein said time intervals are selected from atleast two constant time intervals based on said comparison of said powerdifference to said threshold.
 23. The communication system transmitdiversity method of claim 14, wherein said processor of said firstdevice is to increase a diversity interval parameter in a firstdirection based on an increase in said mobility parameter.
 24. Thecommunication system of claim 23, wherein said processor of said firstdevice is to increase said diversity interval parameter in said firstdirection if said mobility parameter exceeds a threshold value.
 25. Thecommunication system of claim 23, wherein said processor of said firstdevice is to decrease said diversity interval parameter in a seconddirection opposite said first direction based on a decrease in saidmobility parameter.
 26. The communication system of claim 25, whereinsaid processor of said first device is to decrease said diversityinterval parameter in said second direction if said mobility parameterdoes not exceed a threshold value.